1.0 Field of the Invention
This invention relates to electronic ballast systems, and, more particularly, to an electronic ballast system for operating fluorescent lamps with universal input (from 108V to 305V) and having a subsystem with a battery, along with a battery charger, and associated logic that provides for emergency lighting.
2.0 Description of Related Art
Electronic ballast systems for operating fluorescent lamps are well known and some of which are disclosed in U.S. Pat. Nos. 5,808,421 and 6,031,342. Electronic ballast systems typically convert a low frequency alternating current source having a relatively low frequency in the range from 50 to 60 Hz to a higher frequency typically in the range of 30-40 kHz. The conversion commonly involves a two stage process, wherein the ac oscillation having a frequency of 50 to 60 Hz is first rectified to a dc voltage and then this dc voltage is chopped at a higher frequency to produce alternating current in the frequency range of 30-40 kHz, which is used to excite the fluorescent lamp. The electronic ballast circuits advantageously perform the desired function for operating fluorescent lamps and reduce the energy consumption, compared to non-electronic ballast circuits, and especially compared to incandescent lamps. However, the conventional electronic ballast circuits typically employ a preheat operating mode that needs to be completed before the fluorescent lamp is excited so as to sequence it into its continuous and efficient running mode. It is desired that an electronic ballast circuit be provided that eliminates the need for preheating the fluorescent lamp before the fluorescent lamp is rendered operative into its continuous operating and efficient running mode.
Electronic ballast circuits are typically selected to have parameters that operate for particular input frequency oscillation. For example, the electronic ballast circuit may have parameters selected so as to operate with the 110 volt, 60 Hz typically found in the United States, whereas other ballast circuits may have parameters selected to operate with 220 volts, 50 Hz typically found in European countries. It is desired to provide a ballast circuit that operates with the universal input covering the range from between 108 to 305 volts at a frequency range between 50-60 Hz.
Further, it is desired to provide an electronic ballast circuit that handles various types of fluorescent lamps such as, T5, T8, T12, 20W, 32W, 40W, 56W, 70W, linear, circular, or U-shaped type fluorescent lamps.
Because fluorescent lamps have a lower energy consumption compared to incandescent lamps, they are extensively used in industrial and commercial environments, which commonly require emergency lighting. It is desired to provide for electronic ballast system for operating one or more fluorescent lamps and having a subsystem with a battery, along with a battery charger, and associated logic to provide for emergency lighting.
Electronic ballast systems that operate fluorescent lamps are commonly plagued by the disadvantage that they produce electromagnetic interference (EMI) and radio frequency interference (RFI). It is desirable to provide for an electronic ballast system that reduces or even eliminates the EMI/RFI noise commonly produced by the electronic ballast systems.
Electronic ballast circuits commonly employ inductive loads, which act to lower the power factor, which, in turn, increases the consumption of current and, thereby, reduces the efficiency related to fluorescent lamps. It is desirable that an electronic ballast circuit be provided with a power factor correction circuit that allows for the creation of a power factor that approaches unity, thereby furthering the efficiency of the electronic ballast system.
The invention is directed to an electronic ballast system for operating one or more fluorescent lamps with universal input (from 108V to 305V) and having a subsystem with a battery, along with a battery charger and associated logic, that provides for emergency lighting. The electronic ballast system allows for the operation of fluorescent lamps without preheating their cathodes, as well as a circuit for power factor correction that allows electronic circuit to have a power factor that approaches unity.
The electronic ballast system comprises: (a) an EMI filter having an input connected to an electric surge and providing a filtered output; (b) a full-wave rectifier having an input connected to the output of said EMI filter and providing a first d.c. voltage; (c) a power factor correction circuit having an input connected to the output of the full-wave rectifier and providing a power factor regulated output; and (d) a first inverter ballast circuit having an input connected to the output of the power factor converter. The inverter ballast circuit has a sweep frequency circuit for supplying an oscillating current to power a first fluorescent lamp without the need of preheating its cathode.